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-pµe¦WºÙ¡G¦³¾÷ª÷ÄÝ¿ù¦Xª«©x¯à°òÂà´«¤Î¶Ê¤Æ¤ÏÀ³( ¤G) Novel Organometallic Functional Transfor mation
a n d C a t a ly s i s ( I V) -pµe½s¸¹¡GNSC89 -2113-M-002-0 06 °õ¦æ´Á--¡G87 ¦~8 ¤ë1 ¤é¦Ü88 ¦~7 ¤ë31 ¤é ¥D«ù¤H¡G³¯¦Ë«F °õ¦æ¾÷ºc¡G¥xÆW¤j¾Ç¤Æ¾Ç¨t ¤@¡B¤¤¤åºK-n ÍP¤þ°ò¤Î¤þ¤G²m°ò¦³¾÷ª÷ÄÝ¿ù¦X ª«»P²mÓiªº¤ÏÀ³§Î¦¨ «£-l¥Íª«¡C ÃöÁäµü¡GÍP¤þ°ò¡A¤þ¤G²m°ò¡A²mÓi Abstract
The reactions of enamines (ROC)HC
=
CMe(NHi
Pr) with η3-allenyl/propargyl complexes [M(PPh3)2(η3-C3H3)]+ (M = Pd, Pt) result in the formation of the pyrrole derivatives. Such reactions involve the intermediates of central-carbon-substituted
η3
-allyl complexes {M(PPh3)2(η3-CH2 C[C-(COR)
=
CMe(NHiPr)]CH2)}+ which are formed by hydroalkenylation to C3H3 moiety. Keywords: η3-allenyl/propargyl complexes,
enamine.
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The addition of an olefinic C–H bond across an unsaturated carbon-carbon bond is highly interesting from the viewpoint of synthetic methodology [1]. The involvement of transition metal complexes in such processes is often crucial, particularly in the aspect of developing new ways for C–C bond formation [2]. We and other groups have discovered that cationic η3 -allenyl/propargyl complexes generally behave as good carbon electrophiles and are subjected to the addition with a wide variety of nucleophiles containing O, S, Se, N, P, or C donor [3-7]. Meanwhile, such complexes
exhibit keen chemical selectivity. For instance, tertiary amine such as Et3N can be added to [Pt(PPh3)2(η3-C3H3)]+ (3) via C–N bond formation to give a platinacyclobutene adduct [8]. In contrast, 3 activates a phenyl C–H bond in NMe2Ph to succeed arylation, yielding an arylallyl complex [9].
We have chosen to use enamines that are known to contain both active N–H as well as C–H bonds to react with η3-allenyl/propargyl complexes. Our studies lead to the discovery of the first examples of hydroalkenylation to metal complexes of allenyl/propargyl. The insertion of η3-C3H3 to an enamine C–H bond affords a skeleton of "diene" which allows to incorporate with an amino functionality to transform into the pyrrole derivatives.
¤T¡B³ø§i¤º®e
The enamines Me(NHiPr)C=CHR [R = COMe (1a), CO2Me (1b)] have been
prepared respectively by the reactions of α,γ-diketone or ketoester methane with i
PrNH2
[10]. The NMR data of 1a and 1b indicate that tautomerization of eq. 1 overwhelmingly inclines to the enamine form which is presumably stabilized by hydrogen bonding between N–H and the keto group.
N i Pr O H N i Pr O R R R = Me 1a, OMe 1b
Previous studies have shown that amines and amino derivatives with active hydrogen are prone to have regioselective hydroamination to [M(PPh3)2(η3-C3H3)]+ [M = Pd (2), Pt (3)], yielding azatrimethyl-enemethane (N-TMM) complexes and their derivatives [11]. However, heating the mixture of 2 and 1b at 50 ¢J was found to generate the pyrrole derivatives. Deleberate investigation shows that reactions of equimolar amounts of 2 and enamine at 25 ¢J undergo unprecedented hydroalkeny-lation. The regioselective C–C coupling takes place between the central carbon of the C3H3 and the β-olefinic carbon of the enamine, and results in the enamine-allyl complexes in the formula of Pd(PPh3)2{η3 -CH2C[C(COR)CMe(NHiPr)]-CH2}+
[R = Me (4a), OMe (4b)] with the yields over 75%. Complexes 4a and 4b were mainly characterized by NMR techniques as well as elemental analysis. Either heating the reaction solutions of complexes 4a and 4b to 50 ¢J, or treating them with base, the products of pyrrole derivatives 6a and 6b could be obtained, respectively (Scheme 1).
The analogous reactions of [Pt(PPh3)2(η3 -C3H3)](BF4) (3) with 1a or 1b produced
{Pt(PPh3)2(η3-CH2C[C(COR)
=
CMe(NHi Pr)]-CH2)}(BF4) [R = Me (4a’), OMe (4b’)] alsoin very good yields. The enamne-allyl platinum complexes could be formed alternatively from the reactions of trans-Pt(Br)(PPh3)2(η3-CHCCH2) and enamine at 25 ¢J, however, with longer reaction time. The single-crystal X-ray crystallography provides the authentic molecular structure for
4b’. Figure 1 shows its ORTEP drawing.
The length of C2-C4 is 1.46(2) Å , a typical Csp2
–Csp2
single bond. The dihedral angle between the C1-C2-C3 and C1-Pt-C2 planes is 68(1)º, and ∠C1–C2–C3 is 113(1)º, which are consistent with the η3-allyl characteristic and somewhat approach that of the η3 -trimethylenemethane species [7, 12]. It indicates that there is significant electronic delocalization in the planar N-C5-C4-C10-O1 moiety of enamine. The distance between N and O1 atoms is 2.52 Å that is suitable for hydrogen bonding in the vicinity. However, the generated amino hydrogen points out of the enamine plane with ∠O1– H–N = 116(7)º [13].
Ring closure in 4a’ and 4b’ could be accomplished by heating or treating with base as well, except that cyclization in 4b’ first generates a dihydropyrrole derivative 5b. Upon chromatographing on a silica gel column, 5b would isomerize to the stable pyrrole product 6b. Such a reaction is mechanistically comparable to the furan formation from an enolate-allyl complex [14].
3. Conclusion
The regioselective addition of enamine to the η3-allenyl/propargyl complexes demonstrate a new type of “alkene-alkyne” coupling which affords new enamine-allyl complexes and leads to the formation of pyrrole derivatives. N Ph3P M Ph3P N iPr iPr Me COR M Ph3P Ph3P O H R N i Pr O H R N iPr Me COR Me R = Me 6a, OMe 6b Scheme 1 M = Pd 2, Pt 3 + + R = Me 4a, OMe 4b R = Me 4a', OMe 4b' base or ∆ + M = Pd M = Pt R = OMe 5b
Acknowledgement.
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4. Experimental Section
4.1. General
Commercially available reagents were purchased and used without purification unless necessary. Solvents were dried with use of standard procedures. All reactions and other manipulation were carried out under a nitrogen atmosphere, using standard Schlenk techniques. The IR spectra were recorded on a Bio-Rad FTS-40 spectrophotometer. The NMR spectra were run on either a Bruker AC-200 or ACE-300 spectrometer. For the 31P NMR spectra, the spectrometer frequency at 81.015 or 121.49 MHz was employed, and the chemical shifts are given in ppm (δ) relative to 85% H3PO4 in CDCl3. Values upfield of the standard are defined as negative. The corresponding frequencies for 13C NMR spectra were at 75.47 MHz, respectively. Mass spectrometric analyses were collected on a JEOL SX-102A spectrometer. Elemental analyses were done on a Perkin Elmer 2400 CHN analyzer.
4.2. Synthesis and Characterization
{Pd(PPh3)2(η3
-CH2C[C(COMe)=CMe(NHi
Pr)]CH2)}(BF4)
(4a). The reaction of 2 (300 mg, 0.39 mmol) and (MeOC)HC
=
CMe(NHiPr) (1a) (55 µL, 0.039 mmol) was carried out in 20 mL predried CH2Cl2 at -30 ¢J. After stirring for 90 min, the solution was concentrated to 2 mL. Adding 20 mL of dried Et2O gave yellow solid product. Recrystallization resulted in 4a in 76% isolated yield (260 mg).31 P NMR (CDCl3, 300 MHz) δ 23.8; 1H NMR (CDCl3, 300 MHz) δ 1.21, 1.24 (3H, 3H, s, s, CH3), 2.00 (6H, d, JHH = 6.9 Hz, CH(CH3)2), 3.50 (2H, m, br, Hanti), 3.69 (1H, m, CH(CH3)2), 4.12 (2H, br, Hsyn), 7.02-7.73 (30H, m, phenyl H), 12.6 (1H, d, JHH = 2.2 Hz, NH); 13C NMR (CD3CN, 300 MHz) δ 18.4, 23.7 (CH3), 30.5 (CH2), 46.2 (COCH3), 80.1 (t with virtual coupling, JCP = 15.4 Hz, Ct), 104.2 (Cγ), 129-134 (phosphino phenyl C), 146.1 (Cc), 165.0 (NC
=
C), 193.7 (COMe). MS (FAB, m/z): 810 (M+-BF4). Anal. Calcd for PdC47H48NOP2BF4: C, 62.86; H, 5.38; N, 1.56. Found : C, 62.30; H, 5.04; N, 1.25.{Pd(PPh3)2(η3-CH2C[C(CO2 Me)=CMe-(NHiPr)]CH2)}(PF6) (4b). Refer to 4a for
the procedure. The reaction of 2 (100 mg, 0.12 mmol) and 1b (20 mg, 0.15 mmol) gave yellow solid product in 76% isolated yield (90 mg). IR (KBr pallet) νCO 1638 cm-1; 31 P NMR (CDCl3, 300 MHz) δ 24.53; 1H NMR (CDCl3, 300 MHz) δ 1.15 (6H, d, JHH = 6.4 Hz, CH(CH3)2), 2.04 (3H, CH3), 3.14 (3H, s, OCH3), 3.68 (5H, m, br, CH2(allyl), CH(CH3)2), 6.82-7.64 (30H, m, phenyl H), 10.09 (1H, d, JHH = 2.0 Hz, NH); 13C NMR (CDCl3, 300 MHz) δ 17.7 (CH3), 23.5 (s, (CH3)2CH), 45.3 ((CH3)2CH), 50.9 (OCH3), 78.5 (t, JCP = 15.7 Hz, Ct), 91.2 (MeC
=
C), 128.7, 128.9, 130.1, 130.7, 131.1, 133.7 (phosphino phenyl C), 141.5 (Cc), 164.0 (MeC=
C), 168.8 (CO2Me). MS (FAB, m/z): 826 (M+-PF6). Anal. Calcd for PdC47H48 -NO2P3F6.CH2CH2: C, 55.43; H, 4.75; N,
1.35. Found : C, 54.01; H, 4.63; N, 1.11.
{Pt(PPh3)2(η3-CH2 C[C(COMe)=CMe-(NHiPr)]CH2)}(PF6) (4a’). The reaction of 3 (240 mg, 0.28 mmol) and equimolar
amounts of 1a produced 4a’ in 82% (220 mg). 31P NMR (CDCl3, 300 MHz) δ 18.1 (JPPt = 3828 Hz,); 1H NMR (CDCl3, 300 MHz) δ 2.00 (6H, d, JHH = 6.9 Hz, CH(CH3)2), 2.13, 2.15 (3H, 3H, s, s, CH3), 3.33 (2H, br, Hsyn), 3.45 (2H, dd, JHP = 8 Hz, JHPt = 40.8 Hz, Hanti), 3.77 (1H, m, CH(CH3)2), 7.03-7.76 (30H, m, phenyl H), 12.5 (1H, d, JHH = 2.2 Hz, NH); 13 C NMR (CDCl3, 300 MHz) δ 15.2, 23.4
(CH3), 30.6 (CH2), 45.4 (COCH3), 69.6 (d,
JCP = 34 Hz, JCPt = 105 Hz, Ct), 103.7 (JCPt = 30 Hz, Cγ), 128.0-133.9 (phosphino phenyl C), 143.5 (t, JCP = 4 Hz, JCPt = 20.2 Hz, Cc), 165.1 (NC
=
C), 192.4 (COMe). MS (FAB, m/z): 899 (M+-BF4). Anal. Calcd for PtC47H48NOP2BF4: C, 57.20; H, 4.90; N, 1.42. Found : C, 56.78; H, 4.04; N, 1.20.{Pt(PPh3)2(η3-CH2C[C(CO2 Me)=CMe-(NHi
Pr)]CH2)}(BF4) (4b’). Complex 3 was
first prepared from trans-Pt(Br)(PPh3)2(η3 -CHCCH2) (300 mg, 0.36 mmol) and AgBF4 (69 mg, 0.36 mmol) in situ. The reaction of
3 and 1b (0.36 mmol) basically followed the
procedure as used for the preparation of 4a produced 4b’ in 77% isolated yields (272 mg). Colorless single crystals were obtained by recrysatallization from CH2CH2/benzene. IR (KBr pallet) νCO 1634 cm-1 νC=C 1580 cm-1; 31P NMR (CDCl3, 300 MHz) δ 19.6 (JPPt = 3845 Hz,); 1H NMR (CDCl3, 300 MHz) δ 1.24 (6H, d, JHH = 6.3 Hz, CH(CH3)2), 2.20 (3H, JHPt = 7.2 Hz, CH3), 3.10 (2H, d, JHH = 8.6 Hz, JHPt = 42 Hz, Hanti), 3.20 (3H, s, OCH3), 3.63 (2H, br, Hsyn), 3.77 (1H, dhep, JHH = 6.3, 8.0 Hz, CH(CH3)2), 7.0-7.6 (30H, m, phenyl H), 10.4 (1H, d, JHH = 8.0 Hz, NH); 13C NMR (CDCl3, 300 MHz) δ 15.1 (CH3), 22.6 (s, (CH3)2CH), 45.4 (dd, JCP = 5.8, 14.2 Hz, (CH3)2CH), 50.9 (OCH3), 67.6 (d, JCP = 32 Hz, JCPt = 100 Hz, Ct), 91.6 (JCPt = 27 Hz, MeC
=
C), 128.4-133.4 (phosphino phenyl C), 140.6 (t, JCP = 2.9 Hz, JCPt = 18.4 Hz, Cc), 165.0 (JCPt = 19.0 Hz, MeC=
C), 169.1 (JCPt = 11 Hz, CO2Me). Anal. Calcd for PtC47H48NO2P2BF4: C, 56.29; H, 4.83; N, 1.40. Found : C, 55.74; H, 4.91; N, 1.12. 3-carboxymethyl-2-methyl-4-methylene-N-isopropyldihydropyr role (5b). 1H NMR (C6D6, 200 MHz) δ 1.13 (6H, d, JHH = 6.5 Hz, CH3), 2.31 (3H, s, CH3), 3.61 (3H, s, OCH3), 4.01 (1H, m, JHH = 6.5 Hz, CH), 4.18 (2H, t, JHH = 3.4 Hz, CH2), 4.52, 5.10 (1H, 1H, dt, JHH = 1.5, 3.4 Hz, =CH2). 3-acetyl-2,4-dimethyl-N-isopropyldihy-dropyr role (6a). A solution that contained4a (30 mg) in 2 mL of chloroform was heated at 50 ¢J for 24 h. The solution was then chromatographed on alumina and eluted with Et2O. Compound 6a was obtained in 75%
yield. 1H NMR (CDCl3, 200 MHz) δ 1.34 (6H, d, JHH = 6.6 Hz, CH(CH3)2), 2.38, 2.47 (3H, s, s, CH3), 4.28 (1H, m, JHH = 6.6 Hz, CH(CH3)2), 6.38 (1H, s, =CH). 3-carboxymethyl-2,4-dimethyl-N-isopropylpyr role (6b). 1H NMR (CDCl3, 200 MHz) δ 1.34 (6H, d, JHH = 6.6 Hz, CH3), 2.19 (3H, s, CH3), 2.48 (3H, s, CH3), 3.76 (3H, s, OCH3), 4.27 (1H, m, JHH = 6.6 Hz, CH2), 6.38 (1H, s, =CH); 13C NMR (CDCl3, 300 Hz) 11.1, 12.8, 23.2, 46.6, 50.3, 114.0, 120.4, 128.4, 132.0, 166.9; HRMS: calcd for C11H17NO2 (M+) 194.1181, found 194.1180.
4.3. X-ray crystallographic Analysis.
basis of an experimental ψ rotation curve. The refinement procedure was by a full-matrix least-squares method including all the non-hydrogenic atoms anisotropically. Hydrogen atoms were fixed at the ideal geometry and the C–H distance of 1.0 Å ; their isotopic thermal parameters were fixed to the values of the attached carbon atoms at the convergence of the isotropic refinement. Atomic scattering factors were taken from ref 15. Computing programs are from the NRCC SDP VAX package [16]. Crystallographic data, selected bond parameters of 4b’ are collected in Tables 2 and 3. UK on request, quoting the deposition number 135924.
Acknowledgments We thank the National
Science Council, Taiwan, ROC for the financial support.
Refer ences
[1] J. March, "Advanced Organic Chemistry,
Reactions, Mechanisms, and Structure" John Wiley & Sons, Inc. 4th
Ed., 1992.
[2] C. P. Casey, C. S. Yi, J. Am. Chem. Soc. 114 (1992) 6597.
[3] T.-M. Huang, J.-T. Chen, G.-H. Lee, Y. Wang, J. Am. Chem. Soc. 115 (1993) 1170.
[4] V. Plantevin, P. W. Blosser, J. C.
Gallucci, A. Wojcicki,
Organometallics 13 (1994) 3651. [5] T.-M. Huang, Huang, R.-H. Hsu, C.-S.
Yang, J.-T. Chen, G.-H. Lee, Y. Wang, Organometallics 13 (1994) 3657. [6] F.-Y. Tsai, R.-H. Hsu, J.-T. Chen, G.-H.
Lee, Y. Wang, J. Organomet. Chem. 520 (1996) 85.
[7] J.-T. Chen, Coord. Chem. Rev. 190-192 (1999) 1143 and references therein. [8] J.-T. Chen, Y.-C. Cheng, Y.-K. Chen,
T.-M. Huang, C.-I. Yu, G.-H. Lee, Y. Wang, Organometallic 17 (1998) 2953. [9] J.-T. Chen, R.-H. Hsu, A.-J. Chen, J.
Am. Chem. Soc. 120 (1998) 3243. [10] J. L. Chiara, A Gómez-Sánchez in
“The Chemistry of enamines”, (Ed. Z. Rappoport), John Wiley & Sons, 1994, pp353-358.
[11] N-TMM represents the
azatrimethylenemethane complexes M[CH2C(NR)CH2]. A.-J. Chen, C.-C. Su, F.-Y. Tsai, J.-J. Lee, T.-M. Huang, C.-S. Yang, J.-T. Chen, G.-H. Lee, Y. Wang, J. Organomet. Chem. 569 (1998) 39 and references therein.
[12] A. Wojcicki, New J. Chem. 21 (1997) 733.
[13] The single crystals of 4b’ were obtained by recrystallizing in the CH2Cl2/Et2O solution. Crystal data: Orthorhombic P212121a = 11.100(5)
Å b = 17.764(4) Å , c = 21.951(4) Å , V = 4328(2) Å3, Mo Kα radiation λ= 0.7107
Å
, Z = 4, µ = 3.398 mm-1, 5490 total reflections, 3032 observed reflections (I > 2.0 σ(I )), R = 0.044,Rw = 0.036.
[14] K. Ohe, H. Matsuda, T. Moromoto, S. Ogoshi, N. Chatani, S. Murai, J. Am. Chem. Soc. 116 (1994) 4125.
[15] International Tables for X-ray Crystallography; Kynoch Press: Birmingham, U.K., 1974; Vol. IV. [16] NRC VAX: E. J. Gabe, Y. LePage, J.-P.
Charland, F. L. Lee, P. S. White, J. Appl. Crystallogr. 22 (1989) 384.
